1. Field of the Invention
This invention relates to electrosurgical apparatus and more particularly to a test and control device for electrosurgical apparatus.
2. Prior Art
In electrosurgery, also called surgical diathermy, current of high frequency, herein called diathermy current, is used for cutting tissue and coagulating blood to stop bleeding from cut blood vessels. The diathermy current is passed through the patient via two electrodes, an active electrode having a very small contact surface to concentrate the diathermmy current where it passes into the patient and inactive electrode having a large contact surface to reduce the current density where the diathermy current leaves the patient.
If the inactive electrode does not make good contact with the patient's skin, the diathermy current can cause severe burning of the patient at the inactive electrode. The patient may also be burned if the inactive electrode is not at all connected to the patient or to the diathermy current generator and any part of the patient's body makes contact with grounded metal.
The efficient and safe functioning of electrosurgical apparatus thus depends on an unimpaired return of the diathermy current through the inactive electrode. In order that the risk for burns resulting from failure to connect the inactive electrodes to the diathermy current generator, or from any other discontinuity between the inactive electrode and the diathermy current generator, may be reduced some electrosurgical apparatus include a circuit-testing device which upon manual actuation checks the electrical connection between the patient and the inactive electrode. In such apparatus, the inactive electrode is divided into two segments which are electrically insulated from each other and connected in parallel to the diathermy current generator. The circuit-testing device includes a manually actuated switch which when actuated closes a measuring circuit to pass a low-voltage direct current between the two electrode segments via the adjacent portion of the patient's skin. The magnitude of the current is indicative of the conductivity between the patient's skin and the electrode segments and, hence, the ability of the inactive electrode to provide a good return path for the diathermy current.